Swift heavy ion effects in gallium nitride

GaN layers were irradiated at room temperature with swift heavy ions. AFM (atomic force microscopy) images of specimens irradiated under grazing incidence show tracks. With 74 MeV Kr, the contrast is very faint unlike for 92 MeV Xe and 104 MeV Pb. This behavior indicates that the electronic energy loss threshold to produce tracks at grazing incidence is around 17 keV/nm. These tracks consist of two parts, one with a rather homogeneous contrast, and a second with regularly spaced dots. Measurements in the bulk region after irradiation with 132 MeV Pb ions show tracks with a diameter of about 3 nm.